The present invention relates to a gas filter. In particular, the invention relates to a gas filter primarily intended for use in or with an ostomy appliance.
An ostomy appliance, sometimes called an ostomy bag is a collection bag for receiving drainage from an abdominal opening following surgery, and an ostomy appliance is normally considered to comprise such a bag and means whereby it can be attached to a wearer.
Ostomy bags are well known, one example being shown in British Pat. No. 1,379,464. Since the discharge of the wearer of the bag often contains flatus gases, there have been continuing research and development efforts to devise a satisfactory way of allowing such gases to escape from the interior of the bag in such a way that they are filtered and deodorized. One design of a gas vent appliance or filter is illustrated in British Pat. No. 1,405,032. As shown in that patent, a deodorizing filter comprises a square filter pad comprised of matted fibres and granular activated carbon which may, if desired, be encapsulated in a film made of plastic or other suitable material.
Prior designs of gas filters for ostomy bags, which are sometimes also called ostomy pouches, of gas filters which can be attached to ostomy bags include gas filters which can be attached to bags which were not specially designed to have gas filters. An example is shown in U.S. Pat. No. 4,268,286 entitled ATTACHABLE FILTER AND OSTOMY BAG INCLUDING SAME which issued on May 19, 1981 to P. L. Steer, et al. Such prior designs did not yield a product which could be worn safely when swimming or when taking a shower. In other words, prior designs of ostomy bag filters were not waterproof to the extent desirable. In addition, previously known ostomy bag filters failed to allow passage of an adequate gas flow after being immersed in water.
Accordingly, a gas filter which could be attached to an ostomy bag which was not specially designed for such a filter and which would continue to operate, even after being wetted, would be desirable.